/**
 * This jQuery plugin displays pagination links inside the selected elements.
 * 
 * @author Gabriel Birke (birke *at* d-scribe *dot* de)
 * @version 1.1
 * @param {int}
 *            maxentries Number of entries to paginate
 * @param {Object}
 *            opts Several options (see README for documentation)
 * @return {Object} jQuery Object
 */
jQuery.fn.pagination = function(maxentries, opts) {
	opts = jQuery.extend({
				items_per_page : 10,
				num_display_entries : 10,
				current_page : 0,
				num_edge_entries : 0,
				link_to : "#",
				prev_text : "上一页",
				next_text : "下一页",
				ellipse_text : "...",
				prev_show_always : true,
				next_show_always : true,
				first_text : "第一页",
				last_text : "最末页",
				first_show_always : true,
				last_show_always : true,
				callback : function() {
					return false;
				}
			}, opts || {});

	return this.each(function() {
		/**
		 * Calculate the maximum number of pages
		 */
		function numPages() {
			return Math.ceil(maxentries / opts.items_per_page);
		}

		/**
		 * Calculate start and end point of pagination links depending on
		 * current_page and num_display_entries.
		 * 
		 * @return {Array}
		 */
		function getInterval() {
			var ne_half = Math.ceil(opts.num_display_entries / 2);
			var np = numPages();
			var upper_limit = np - opts.num_display_entries;
			var start = current_page > ne_half ? Math.max(Math.min(current_page
									- ne_half, upper_limit), 0) : 0;
			var end = current_page > ne_half ? Math.min(current_page + ne_half,
					np) : Math.min(opts.num_display_entries, np);
			return [start, end];
		}

		/**
		 * This is the event handling function for the pagination links.
		 * 
		 * @param {int}
		 *            page_id The new page number
		 */
		function pageSelected(page_id, evt) {
			current_page = page_id;
			drawLinks();
			var continuePropagation = opts.callback(page_id, panel);
			if (!continuePropagation) {
				if (evt.stopPropagation) {
					evt.stopPropagation();
				} else {
					evt.cancelBubble = true;
				}
			}
			return continuePropagation;
		}

		/**
		 * This function inserts the pagination links into the container element
		 */
		function drawLinks() {
			panel.empty();
			var interval = getInterval();
			var np = numPages();
			// This helper function returns a handler function that calls
			// pageSelected with the right page_id
			var getClickHandler = function(page_id) {
				return function(evt) {
					return pageSelected(page_id, evt);
				}
			}
			// Helper function for generating a single link (or a span tag if
			// it'S the current page)
			var appendItem = function(page_id, appendopts) {
				page_id = page_id < 0 ? 0 : (page_id < np ? page_id : np - 1); // Normalize
																				// page
																				// id
																				// to
																				// sane
																				// value
				appendopts = jQuery.extend({
							text : page_id + 1,
							classes : ""
						}, appendopts || {});
				var lnk;
				if (page_id == current_page) {
					lnk = $("<span class='current'>" + (appendopts.text)
							+ "</span>");
				} else {
					lnk = $("<a>" + (appendopts.text) + "</a>").bind("click",
							getClickHandler(page_id)).attr('href',
							"javascript:void(null);");
					// .attr('href', opts.link_to.replace(/__id__/,page_id));

				}
				if (appendopts.classes) {
					lnk.addClass(appendopts.classes);
				}
				// window.alert("appendopts.classes="+appendopts.classes);
				panel.append(lnk);
			}
			// first_text
			if (opts.first_text && (current_page > 0 || opts.first_show_always)) {
				appendItem(0, {
							text : opts.first_text,
							classes : "prev"
						});
			}
			// Generate "Previous"-Link
			if (opts.prev_text && (current_page > 0 || opts.prev_show_always)) {
				appendItem(current_page - 1, {
							text : opts.prev_text,
							classes : "prev"
						});
			}

			// Generate starting points
			if (interval[0] > 0 && opts.num_edge_entries > 0) {
				var end = Math.min(opts.num_edge_entries, interval[0]);
				for (var i = 0; i < end; i++) {
					appendItem(i);
				}
				if (opts.num_edge_entries < interval[0] && opts.ellipse_text) {
					jQuery("<span>" + opts.ellipse_text + "</span>")
							.appendTo(panel);
				}
			}
			// Generate interval links
			for (var i = interval[0]; i < interval[1]; i++) {
				appendItem(i);
			}
			// Generate ending points
			if (interval[1] < np && opts.num_edge_entries > 0) {
				if (np - opts.num_edge_entries > interval[1]
						&& opts.ellipse_text) {
					jQuery("<span>" + opts.ellipse_text + "</span>")
							.appendTo(panel);
				}
				var begin = Math.max(np - opts.num_edge_entries, interval[1]);
				for (var i = begin; i < np; i++) {
					appendItem(i);
				}

			}
			// Generate "Next"-Link
			if (opts.next_text
					&& (current_page < np - 1 || opts.next_show_always)) {
				appendItem(current_page + 1, {
							text : opts.next_text,
							classes : "next"
						});
			}
			// last_text
			if (opts.last_text
					&& (current_page < np - 1 || opts.last_show_always)) {
				appendItem(np, {
							text : opts.last_text,
							classes : "next"
						});
			}
		}

		// Extract current_page from options
		var current_page = opts.current_page;
		// Create a sane value for maxentries and items_per_page
		maxentries = (!maxentries || maxentries < 0) ? 1 : maxentries;
		opts.items_per_page = (!opts.items_per_page || opts.items_per_page < 0)
				? 1
				: opts.items_per_page;
		// Store DOM element for easy access from all inner functions
		var panel = jQuery(this);
		// Attach control functions to the DOM element
		this.selectPage = function(page_id) {
			pageSelected(page_id);
		}
		this.prevPage = function() {
			if (current_page > 0) {
				pageSelected(current_page - 1);
				return true;
			} else {
				return false;
			}
		}
		this.nextPage = function() {
			if (current_page < numPages() - 1) {
				pageSelected(current_page + 1);
				return true;
			} else {
				return false;
			}
		}
		// When all initialisation is done, draw the links
		drawLinks();
	});
}
